Chemosensitization of bladder carcinoma cells by bcl-xL antisense oligonucleotides

Purpose: We investigated antisense inhibition of anti-apoptotic bcl-xL and bcl-2 proteins to increase chemosensitization in the T24 and 5637 bladder carcinoma cell lines. Materials and Methods: A T24 bladder carcinoma cell line stably over expressing bcl-xL protein was constructed. Apoptosis by cytotoxic agents was estimated by cell cycle analysis and Annexin V binding. To eliminate bcl-xL,expression T24 and 5637 cells were treated with C5-propynylated and 2'-O-methylribo-oligonucleotides. Levels of protein and messenger RNA were measured by Western and Northern blot analysis. Cell viability after combined treatment with oligonucleotides and various cytotoxic agents was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and evaluated statistically by Student's 2-sample t test. Results: Forced over expression of bcl-xL protein desensitized the T24 bladder carcinoma cell line to cytotoxic agents. C5-propynylated and 2'-O-methylribo-oligonucleotides down-regulated bcl-xL protein expression in the T24 and 5637 cell lines, and increased their sensitivity to cytotoxic agents. The efficiency of antisense down-regulation of bcl-xL protein expression depended on the type of delivery agent. Conclusions: Antisense down-regulation of bcl-xL protein sensitizes bladder carcinoma cells to cytotoxic agents. However, it is possible that cellular chemosensitization results from a combination of effects, including nonsequence specificity, irrelevant cleavage and effects of the carriers combined with the specific antisense effects.